The present invention relates to rotary pumps or compressors, and more particularly to dry air rotary pumps or compressors suitable for use as a vacuum pump, wherein a rotor is eccentrically mounted within a stator housing and co-operates with the inner peripheral wall of the stator housing and with suitable end wall structure to form suction and compression or delivery chambers so as to generate compressed air or vacuum.
One of the inventors previously introduced a dry air rotary pump or compressor of the type in which a pair of flexible diaphragm type sealing plates are hermetically clamped on the opposite ends of a stator housing by end wall structures to be pressedly contacted with the opposite end faces of a rotor driven within the pump cavity so as to provide the sealing between the suction and compression or delivery chambers of the pump. In use of the rotary pump or compressor, it is necessary to ensure the volumetric efficiency of the pump that the flexible sealing plates are constantly pressed without any lubricating medium against the opposite end faces of the rotor due to the difference between internal pressure generated within the pump cavity and external pressure applied to the outside faces of the sealing plates.
One of the problems experienced in development of the pump or compressor is that the sealing plates are inevitably defaced by friction with the rotor to reduce the volumetric efficiency of the pump or compressor. Another problem is that the end-face sealing contacts of the sealing plates against the opposite end faces of the rotor are greatly influenced by flexibility and elasticity of the sealing plates.